1. Field of the Invention
The present invention relates to a thermally-assisted magnetic recording head including a plasmon generator and a magnetic pole.
2. Description of the Related Art
Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and magnetic recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head section including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head section including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the magnetic recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the magnetic recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
To solve the aforementioned problems, there has been proposed a technology so-called thermally-assisted magnetic recording. The technology uses a magnetic recording medium having high coercivity. When writing data, a write magnetic field and heat are applied almost simultaneously to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization. Hereinafter, a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.
In thermally-assisted magnetic recording, near-field light is typically used as a means for applying heat to the magnetic recording medium. A known method for generating near-field light is to use a plasmon generator, which is a piece of metal that generates near-field light from plasmons excited by irradiation with light. The light for use in generating near-field light is typically guided through a waveguide, which is provided in the slider, to the plasmon generator disposed near a medium facing surface of the slider.
U.S. Patent Application Publication No. 2011/0170381 A1 discloses a technology in which the surface of the core of the waveguide and the surface of the plasmon generator (metallic structure) are arranged to face each other with a gap therebetween, so that evanescent light that occurs from the surface of the core based on the light propagating through the core is used to excite surface plasmons on the plasmon generator to generate near-field light based on the excited surface plasmons.
A thermally-assisted magnetic recording head that employs a plasmon generator as a source of generation of near-field light is configured so that the write head section includes the plasmon generator and a magnetic pole that produces a write magnetic field. The plasmon generator and the magnetic pole are located in close proximity to each other. Now, a description will be made as to the problems with the thermally-assisted magnetic recording head having such a configuration.
Part of the energy of the light guided to the plasmon generator through the waveguide is transformed into heat in the plasmon generator. The plasmon generator, and the magnetic pole located in its vicinity, therefore increase in temperature during the operation of the thermally-assisted magnetic recording head.
Now, a case will be contemplated where the plasmon generator and the magnetic pole are in contact with each other. In this case, as the plasmon generator and the magnetic pole increase in temperature as mentioned above, a noticeable diffusion of substance tends to occur in the plasmon generator and the magnetic pole, causing the materials forming the plasmon generator and the magnetic pole to be diffused into each other. Such interdiffusion may cause the plasmon generator to be reduced in efficiency of transformation of the light that has been guided to the plasmon generator through the waveguide into near-field light. Furthermore, the magnetic pole may also deteriorate in magnetic property, and this may lead to degradation of the characteristics of the write head section.
U.S. Patent Application Publication No. 2011/0170381 A1 discloses a structure in which the plasmon generator and the magnetic pole are not in contact with each other and the plasmon generator is surrounded with a dielectric material. In this structure, the dielectric material is interposed between the plasmon generator and the magnetic pole. However, the adhesion between the plasmon generator and the dielectric material and that between the magnetic pole and the dielectric material are low in this structure. Consequently, in the process of manufacturing the thermally-assisted magnetic recording head or when the plasmon generator and the magnetic pole increase in temperature as mentioned above, there may occur a separation between the plasmon generator and the dielectric material and/or between the magnetic pole and the dielectric material.